Masks are effective but here's how a study from a respected group was misinterpreted to say they weren't

"It's not a study of the mask but of intervention to get people to wear a mask."

March 14, 2023, 5:42 PM

Recently, a review from the Cochrane Library set off a firestorm after headlines declared research published by the respected organization's study found masks don't work and don't stop community transmission of respiratory viruses like COVID-19.

Over a two-month period, some commentators and politicians took to op-ed pieces and social media to say the study proved masks weren't needed the whole time and that mandates had been ineffective.

However, the editor-in-chief of the Cochrane Library, Dr. Karla Soares-Weiser, issued a statement on March 10 to say the analysis had been misinterpreted and that the review didn't find that masks do not work.

Rather it looked at how effective masking programs, like mandates, were at slowing the spread of respiratory viruses and, from there, found the results to be inconclusive.

"Many commentators have claimed that a recently updated Cochrane Review shows that 'masks don't work,' which is an inaccurate and misleading interpretation," Soares-Weiser wrote. "It would be accurate to say that the review examined whether interventions to promote mask wearing help to slow the spread of respiratory viruses, and that the results were inconclusive."

Experts told ABC News the findings from the meta-analysis from the Cochrane Library have not been accurately represented and that evidence shows masks do help prevent the spread of COVID-19.

How the Cochrane review addressed different questions

The Cochrane review, published in late January, looked at several studies that had examined physical interventions to reduce the spread of respiratory viruses.

Many of the studies analyzed looked at masking interventions, meaning how effective masks are if people are given masks and information about masking, and encouraged to wear them.

A sign on a store entrance asks people to wear masks, April 15, 2022, in Philadelphia.
Spencer Platt/Getty Images, FILE

However, giving people masks does not necessarily mean that people will wear masks.

"The study was misinterpreted and, when you give it a very quick glance, you see how that would happen," Dr. Jessica Justman, an associate professor of medicine in epidemiology at Columbia Mailman School of Public Health, told ABC News. "It's looking at interventions that tried to promote the use of different kinds of protective equipment, such as masks, and the outcomes are all going to depend on how well people actually adhere to the particular type of protective equipment."

She continued, "So, it's not as much a study of the mask but a study of the intervention to get people to wear a mask."

Additionally, many of the studies analyzed in the Cochrane review didn't look at whether people were wearing them all the time, like a at home around others, and if they were wearing them properly, including tight-fitting and covering the nose and mouth.

"Masks work if you wear them," Justman said. "But if you wear them very imperfectly, if you wear them in a way where they are only loosely fitting on your face and you take them off, let's say in a crowded restaurant to eat a meal, you can't then conclude when you get COVID that the mask didn't protect you because if you don't wear the mask properly, you're not going to get the full protection."

Ramifications of people misinterpreting the results

Because the review was misinterpreted to say masks don't work rather than the results being inconclusive, Dr. Bruce Y. Lee, a professor of health policy and management at City University of New York School of Public Health, said this could influence people to believe they don't need to wear a mask, which could have consequences.

"This has potential ramifications like long COVID, potential hospitalization and we have to wonder how many lives could have been saved, hospitalizations could have been averted how many cases of long COIVD be avoided if masks were more prevalent," he said.

Lee added it helps that the editor-in-chief issued the statement, but worried the misinterpretation has already been widely spread and it will be hard to change people's minds.

PHOTO: Commuters walk on a street in Tokyo, March 13, 2023, on the first day of reduced mask requirements.
Commuters walk on a street in Tokyo, March 13, 2023, on the first day of reduced mask requirements. Japan's government eased its mask guidelines on March 13, recommending them only on crowded trains and in hospitals or care homes.
Kazuhiro Nogi/AFP via Getty Images

"The concern is that the initial message has already been amplified and the degree to which it was amplified was significant," he said. "One of the challenges is, once information gets out there, it takes twice, triple, sometimes quadruple, or even more than that, the effort to try to correct information that's already out there."

What the science tells us about masks

"We already have information from other studies that show almost a dose-response relationship between wearing no mask at all, wearing a cloth mask, wearing a surgical mask and wearing an N95," Justman said. "As you go up the ladder, so to speak, with each step of a better-quality mask, you see more protection."

One example is a study published in February 2022 by the Centers for Disease Control and Prevention examining those who said they wore masks all the time in indoor public settings.

Researchers found cloth masks were associated with a 56% decrease in testing positive for COVID-19, surgical masks by 66% and N95/KN95 masks by 83% compared to those who didn't wear masks or face coverings.

Lee added that masks are population-based interventions, not individual-based interventions, meaning their efficacy depends on not just one person wearing a mask but how many people are wearing masks too.

"We know that masks not only protect the wearer from other people and from the virus, but they also protect other people from the wearer, because if someone's infectious and shedding the virus, the mask can prevent them from spewing the virus into air, or at least reducing the amount of virus the air," he said.

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